A resistance temperature detector (RTD) is a sensing element that works on the principle of the temperature coefficient of the electrical resistance of metals. These types of sensors provide a change in resistance proportional to a change in temperature. A known electrical current passed through the element produces a voltage drop across the sensing element. This voltage drop can then be measured by a calibrated device to determine the temperature change.
Generally, a RTD is used to monitor a temperature at a point. If a temperature reading is needed over an area in a device, multiple sensors are used resulting in a complex system that adds cost and size to the device.
What is needed is a RTD that monitors temperature beyond a single point and has a small form factor.